Earlier in the day, Jacobs, who injured his left knee during the 49ers’ 20-9 preseason loss to the Texans on Saturday, had written to fans that he “felt good” and was waiting to undergo his MRI.

Jacobs was assisted off the field by Harbaugh and trainer Jeff Ferguson and was later taken to the locker room on a cart.

After the game, Jim Harbaugh said Jacobs had not sustained damage to his anterior cruciate ligament or his patella. Harbaugh said his injury would not be season-ending, but he would miss “a little time.”

Based on Jacobs’ tweets, he might miss even less time than anticipated.